Device and method for lumbar interbody fusion

ABSTRACT

A method for performing percutaneous interbody fusion is disclosed. The method includes the steps of inserting a guide needle posteriorly to the disc space, inserting a dilator having an inner diameter slightly larger than the outer diameter of the guide needle over the guide needle to the disc space to enlarge the disc space, and successively passing a series of dilators, each having an inner diameter slightly larger than the outer diameter of the previous dilator, over the previous dilator to the disc space the gradually and incrementally increase the height of the disc space. Once the desired disc height is achieved, the guide needle and all the dilators, with the exception of the outermost dilator, are removed. An expandible intervertebral disc spacer is then passed through the remaining dilator and positioned in the disc space. Th disc spacer is expanded to the required disc height, and then a bone matrix is passed through the dilator to fill the disc space. The dilator is then removed. An expandible intervertebral disc spacer is also disclosed, having a tapered bore that causes greater expansion of one end of the spacer with respect to the other. A kit for performing the percutaneous interbody fusion procedure is also disclosed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a device and method forperforming interbody spinal fusion, stabilization and restoration of thedisc height in the spine, and in particular to a device and method forperforming percutaneous, minimally invasive interbody fusion of thelumbar spine.

[0003] 2. Discussion of the Related Art

[0004] Many devices exist to assist in maintaining the position of thelumbar vertebra in conjunction with lumbar fusion surgery. Fusion is thejoining together of the vertebra of the spine. The underlying concept ofthe known devices is to maintain the relative position of the vertebralbodies with respect to each other, while the bone that has been placedbetween the vertebra to form the fusion of the vertebra, has anopportunity to heal and mature. These devices employ differentstrategies and philosophies, and can include devices which utilize thepedicles, as well as devices which are placed in to the disc space topromote fusion across the disc space. The latter devices and techniquesassociated with these devices are known as “interbody fusion”. While nosingle technique has been universally accepted as the most optimummethod, there is growing evidence that interbody fusion may be thepreferred method.

[0005] The interbody fusion procedure may be performed via an anterioror posterior approach. Initially, all interbody fusion procedures wereaccomplished using the posterior approach. The procedure was performedby first performing a laminectomy, removing the disc space, and thenpacking the disc space with pieces of bone, which were then permitted toheal over time. The hope was that the inserted bone pieces would growand fuse together with the vertebra above and below that disc space,forming a bridge of bone between the two vertebral bodies, thusaccomplishing the interbody fusion.

[0006] Posterior interbody fusion procedures are accomplished via avariety of techniques. Most procedures attempt to restore proper discheight, i.e. the space between the adjacent vertebra. The patientbenefits from restoring the proper disc height, particularly where therehas been deterioration, degeneration or collapse of the disc.

[0007] More recently, the anterior interbody fusion procedure has gainedpopularity, due to the availability and improvements made in devicesthat enable the anterior approach for lumbar interbody fusions. Thesedevices typically provide for a retroperitoneal or transperitonealtechnique to be used for approaching the lumbar disc, removing some orall of the disc, and placing either bone or a metallic device into thedisc space. These devices also typically provide a means for distractingthe disc space, i.e. making the space between the discs wider.Presently, this aspect of lumbar interbody fusion procedures areconsidered to be an important step in the procedure because of itseffects on the neural foramina, or areas from which the nerve roots exitthrough the vertebra. It is generally accepted that enlarging the discspace consequently enlarges the neural foramina, thus decompressing theexiting nerve roots.

[0008] The current techniques, due to the present equipment available,particularly for anterior interbody fusion, suffer the disadvantage inthat they are major surgeries and require large incisions with themanipulation of both tissue and organs. While attempts have been made toperform anterior interbody fusions laparoscopically, these proceduresare often complicated and are typically performed under generalanesthesia.

[0009] Therefore, a need exists for a method for performing interbodyfusions that reduces the trauma to the patient, and consequentlyreducing recovery time. A device is also needed to facilitate theinterbody fusion procedure to enable the procedure to be performedpercutaneously, enabling the surgeon to distract the disc to restoredisc height, maintain the distraction, and promote the growth of thebone placed in the disc space between the two vertebral bodies, thusaccomplishing the interbody fusion.

SUMMARY OF THE INVENTION

[0010] It is, therefore, an object of the present invention to provide aminimally invasive, percutaneous surgical procedure for performinginterbody fusion which reduces the trauma to the patient and reducesrecovery time.

[0011] It is also an object of the present invention to provide apercutaneous interbody fusion procedure which accomplishes the interbodyfusion through small incisions in the body of the patient and utilizes aminimum of incisions to complete the procedure.

[0012] It is a further object of the present invention to provide adevice which facilitates the percutaneous interbody fusion procedure.

[0013] It is yet another object of the present invention to provide adevice which distracts the disc space and which may be inserted througha tube to effect the percutaneous interbody fusion procedure.

[0014] It is a further object of the present invention to provide acollapsible and expandible interbody fusion spacing device thatfacilitates the percutaneous interbody fusion procedure.

[0015] It is still a further object of the present invention to providea kit for performing a minimally invasive percutaneous interbody fusionprocedure.

[0016] The above and other objects of the present invention may beachieved by providing a collapsible and expandible interbody fusionspacer device that may be inserted through a small diameter tube to thedisc space that is being fused, so that the procedure may be performedin a minimally invasive manner. The spacer is preferably constructed intwo halves that are connected by pins located on the sides of thespacer. The outer surface may be flat to engage the end plate of thevertebra above and below the spacer, and the outer surface may bescored, have ridges, points, tabs, detents, or the like to enhancegripping of the end plates of the vertebra to resist movement of thespacer once it is in place. The interior surfaces of the halves thatmake up the spacer include a semicircular hollowed portion that ispreferably threaded along at least a portion of its length that isaligned with a similar semicircular threaded hollowed portion on theother half of the spacer. When the spacer is assembled, the threadedportion forms a canal for acceptance of a piston screw. Preferably, thethreaded canal is tapered from one end to the other, particularly fromthe end which will be positioned posteriorly in the disc space to theend which will be positioned anteriorly in the disc space. When thepiston screw is inserted, the anteriorly positioned end will expand agreater distance in the disc space than the posterior end, due to thetapered threaded canal. This will cause the disc height, i.e. thedistance between the vertebra, to be greater anteriorly thanposteriorly, which more closely mimics the natural curve of the spine,particularly in the lumbar spine, thus restoring lordosis, the naturalcurve of the lumbar spine.

[0017] A method for performing percutaneous interbody fusion is alsoprovided, in which the disc space is enlarged in the craniocaudaldirection following percutaneous discectomy. Following the discectomy, aguide needle is passed through the incision to the disc space betweenthe vertebra. Over the needle, a series of tubularly shaped dilators arepassed, with each successive dilator having an inner diameter that isslightly larger than the outer diameter of the dilator that is in place.As each successive dilator is inserted in the disc space, it forces thevertebra apart, increasing the disc space, until a desired heightbetween the vertebra is achieved. Once a desired height is reached,which is only a desired height and not necessarily the maximum height,the outer dilator is left in place, while those inside the outer dilatorare removed. The maximum height does not have to be achieved by thedilators because the expandible intervertebral disc spacer of thepresent invention is then inserted into the disc space through the outerdilator. Once in place, the spacer is expanded to increase the discheight to the maximum distance. After the spacer is in place on one sideof the vertebral body, the procedure is repeated on the other side.After the two spacers are in place, a bone matrix, which encouragesfusion, is passed through the dilators, filling the space with bone. Thedilators are then removed and the procedure is complete.

[0018] A kit for performing percutaneous interbody fusion is alsoprovided, which includes a plurality of expandible intervertebral discspacers, which preferably expand the disc space a greater distanceanteriorly than posteriorly, at least one dilator for expanding the discheight and having a hollow interior for allowing passage of the discspacers to the disc space, and a guide needle. A curette for performingpercutaneous discectomies may be provided, and a bone matrix for fusingthe vertebra together may also be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of thepresent invention will become more readily apparent from the followingdetailed description of preferred embodiments of the invention, taken inconjunction with the accompanying drawings, in which:

[0020]FIG. 1 illustrates a perspective view of an expandibleintervertebral disc spacer according to the present invention;

[0021]FIG. 2 illustrates a side cross-sectional view of the disc spacerof FIG. 1;

[0022]FIG. 3 illustrates a perspective view of an alternative embodimentof the expandible intervertebral disc spacer of FIG. 1;

[0023]FIG. 4 illustrates a side cross-sectional view of the disc spacerof FIG. 3;

[0024]FIG. 5 illustrates diagrammatic view of a dilator system forenlarging the disc height of the vertebra prior to placement of the discspacer of the present invention between the vertebra;

[0025]FIG. 6 illustrates a diagrammatic view of the placement procedureof the disc spacer of the present invention;

[0026]FIG. 7 illustrates a diagrammatic view of the disc spacer in placebetween the vertebra and in a fully expanded condition to restore thenatural curvature of the spine;

[0027]FIG. 8 illustrates a percutaneous interbody fusion kit accordingto the present invention; and

[0028] FIG.9 illustrates a flow chart of the percutaneous interbodyfusion method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Referring now to the drawings, in which like reference numeralsidentify similar or identical elements throughout the several views, andinn particular to FIG. 1, there is shown the expandible intervertebraldisc spacer device 10 according to the present invention. Preferably,the disc spacer 10 is comprised of two similarly shaped halves 12, 14that are opposed to each other and loosely connected by pins 16. Theouter surface of each half may be scored, as indicted by referencenumeral 22, for facilitating adherence to the end plates of thevertebral bodies between which disc spacer 10 is placed. When top half12 and bottom half 14 are assembled, together they may form a cylinder,a cube, a rectangular box, or any geometric shape that may be split toform two opposed halves. A tapered bore 18 is provided, which has alarger diameter 30 at a first end and a smaller diameter 32 at a secondend. Preferably, tapered bore 18 is threaded over at least a portion ofits length. While disc spacer 10 is preferably constructed of titaniumor other suitable metal alloy, cortical bone may also be used. It isalso contemplated that the material of the disc spacer 10, or at leastthe material of which tapered bore 18 is constructed, is self-tapping sothat threads are not needed.

[0030] Screw 20 is provided for insertion into bore 18 to expand thedisc spacer 10. As seen in FIG. 2, pins 16 are located in pin bores 26which have a larger diameter near the outer surface of disc spacer 10,and a smaller diameter near the interior of the spacer. The change indiameter creates a stop 34 which engages the head 24 of pins 16, toterminate expansion of the spacer 10. When screw 20 is inserted intobore 18, the smaller diameter 32 of the threaded bore causes a greaterexpansion at the second end than at the first, for reasons which will bedescribed below.

[0031]FIGS. 3 and 4 illustrate an alternative embodiment of the discspacer 40 of the present invention. Disc spacer 40 comprises a pair ofopposed plates 42, 44 which may be square, rectangular, rhomboidal,trapezoidal, or any suitable geometric shape. Pins 16 loosely hold theplates together, as described above, through pin bores 26, which includelarger diameter portion 28 which creates stop 34 to engage the head 24of pins 16. The outer surface of plates 42, 44 may include ridges 50,detents, scoring or the like to enhance adherence to the end plates ofthe vertebra. Each plate includes a threaded ledge portion 48, whichforms a bore for accepting screw 20 when the plates are assembled toform disc spacer 40. Preferably, the threaded portion has a largerdiameter at a first end 52 and a smaller diameter at a second end 54, sothat there is greater expansion of the spacer at the second end 54 thanat first end 52, for reasons which will be described below.

[0032]FIGS. 5, 6 and 7 illustrate the percutaneous interbody fusionprocedure of the present invention, utilizing the expandibleintervertebral disc spacer of the present invention. Following apercutaneous discectomy in which the disc between vertebra 64 and 66 isremoved, preferably posteriorly, through a small incision, disc space 62is enlarged using dilator system 60 in the procedure according to thepresent invention. In the procedure, a guide needle 68 is inserted intothe disc space under scanning imaging, preferably fluoroscopy. Once theguide needle 68 is in place in the disc space 62, a series of dilators70 are inserted over guide needle to enlarge the disc space. A firstdilator 72, having an inner diameter that is slightly larger than theouter diameter of guide needle 68 is passed over the guide needlethrough the incision until it reaches the disc space 62. A seconddilator 74, having an inner diameter that is slightly larger than theouter diameter of first dilator 72 is then passed over dilator 72 untilit reaches disc space 62. A third dilator 76, a fourth dilator 78 and afifth dilator 80, each having successively larger inner diameters, arethen passed over the previous dilator into the disc space 62. As eachdilator enters the disc space, it gradually and incrementally enlargesthe height of disc space 62 until the disc space is at a desired height.The desired height does not have to be the maximum required height,since that height may be reached by the expandible disc spacer whichwill be inserted into the disc space. The number of dilators may ofcourse vary, depending on the height of the disc space desired. Thedepth to which the dilators are inserted can be monitored in many knownways, such as by fluoroscopy, calibrations on the dilators, acombination of both, or other means.

[0033] Referring to FIG. 6, once the dilators are in place, and the discspace 62 is at the desired height, the guide needle 68 and all thedilators, with exception of the outermost dilator 80, are removed.Expandible intervertebral disc spacer 10 is the passed through dilator80 to the disc space 62 by an insertion tool 82. The position of discspacer 10 is confirmed under fluoroscopy, and either tool 82 or anothertool inserted through dilator 80 is used to tighten screw 20. Discspacer 10 is positioned so that the first end of spacer 10, having thelarger diameter 30 of tapered bore 18, is positioned posteriorly, whilethe second end having smaller diameter 32 of bore 18 is positionedanteriorly. As seen in FIG. 7, when the screw 20 is tightened, thesecond end, on the anterior side of the spine. opens a distance D2,which is greater than distance D1, which is on the posterior side of thespine. This restores lordosis, or the natural curvature of the spine,particularly in the lumbar region, and relieves the intervertebralforamina and decompresses the nerve roots. Once the disc spacer 10 is inposition, bone matrix is passed through the dilator 80 to encouragefusion, to fill the disc space with bone.

[0034] While the above procedure has been described for only one set ofdilators, and for enlarging the disc space for placement of a discspacer on one side of the disc space 62, it is understood that theprocedure is performed on both sides of the disc space to raise the discheight evenly, and that two disc spacers 10 are inserted. After the bonematrix is inserted, the dilators are then removed and the procedure iscomplete.

[0035]FIG. 8 illustrates a kit for performing the percutaneous interbodyfusion procedure of the present invention. Kit 90 comprises a packagehaving top cover 92 and bottom cover 94, where top cover 92 ispreferably formed of plastic having depressions or indentations 96 forholding the instruments packaged therein. Packaged in kit 90 arepreferably at least two disc spacers 10, a corresponding number ofscrews 20, a plurality of dilators 70 and a guide needle 68. Kit 90 ispreferably sterilized.

[0036]FIG. 9 is a flow chart of the method of the present invention.Following a percutaneous discectomy procedure, a guide needle isinserted through the incision at step 100 to the disc space between thevertebral bodies to be fused. The depth to which the guide needle isinserted is observed, preferably through fluoroscopy, in step 102. Oncethe guide needle is in place, a dilator having an inner diameter that isslightly larger than the outer diameter of the guide needle is passedover the guide needle to the disc space in step 104. The dilatorincreases the height of the disc space. In step 106, a second dilator ispassed over the first dilator, where the second dilator has an innerdiameter that is slightly larger than the outer diameter of the firstdilator, to further increase or enlarge the disc space. At step 108, theheight of the disc space is then observed, preferably throughfluoroscopy, to see if it is at the desired height, at step 110. If not,the procedure returns to step 106 and another dilator, having an innerdiameter slightly larger than the outer diameter of the previousdilator, is passed over the previous dilator to the disc space. If thedisc space is at the desired height, the guide needle and all thedilators, with the exception of the outermost dilator, are removed atstep 112. At step 114, an expandible intervertebral disc spacer isinserted through the dilator to the disc space. The position of the discspacer is adjusted to a proper position at step 116, and then observed,preferably through fluoroscopy, at step 118. If it is determined at step120 that the disc spacer is not at the correct location, the procedurereturns to step 116. If the position is correct, the disc spacer isexpanded to enlarge the disc space to a desired height at step 122. Ifit is determined at step 124 that the space is not at the desiredheight, the procedure returns to step 122. If the space is at thedesired height, the tool is removed at step 126, and a bone matrix ispassed down the dilator to the disc space in step 128. Once the bonematrix is in place, the dilator is removed at step 130, and the incisionis closed at step 132, ending the procedure.

[0037] While the invention has been shown and described with referenceto certain preferred embodiments, it will be understood by those skilledin the art that various changes and modifications in form and detail maybe made therein without departing from the spirit and scope of theinvention, as defined by the appended claims.

What is claimed is:
 1. A method for performing a percutaneous interbodyfusion procedure following a percutaneous discectomy procedure,comprising the steps of: inserting a guide needle through an incision ina patient's body to a position in the disc space between a first andsecond vertebra; inserting a dilator over the guide needle to enlargethe disc space to a first desired height; removing the needle from thedilator; inserting an expandible intervertebral disc spacer into thedisc space through the dilator; expanding the disc spacer to enlarge thedisc space to a second desired height; inserting a bone matrix compoundinto the disc space through the dilator; removing the dilator; andclosing the incision.
 2. The method of claim 1, wherein the guideneedle, the dilator, the disc spacer, and the bone matrix compound areinserted posteriorly of the spine of the patient.
 3. The method of claim1, wherein the steps of inserting the guide needle, the dilator, and thedisc spacer are observed under imaging techniques including fluoroscopy.4. The method of claim 1, wherein an inner diameter of the dilator isslightly larger than an outer diameter of the guide needle.
 5. Themethod of claim 4, further comprising the step of successively insertinga plurality of dilators over a previous dilator to enlarge the discspace to the first desired height.
 6. The method of claim 5, whereineach successive dilator has an inner diameter that is slightly largerthan an outer diameter of a previous dilator.
 7. A method for performinga percutaneous interbody fusion procedure after removal of a disc,comprising the steps of: inserting a guide needle through an incision inthe patient's body to a position in the disc space between a first andsecond vertebra on a first lateral side if the patient's spine;inserting a first dilator having an inner diameter that is slightlylarger than an outer dameter of the guide needle over the guide needleto the disc space to enlarge the disc space; determining if the discspace is at a first desired height; if the disc space is not at thefirst desired height, successively inserting a plurality of dilatorsover the first dilator and guide needle, each successive dilator havingan inner diameter that is slightly larger than an outer diameter of aprevious dilator to enlarge the disc space to the desired first height;if the disc space is at the first desired height, removing the guideneedle and each dilator except for an outermost dilator; inserting anexpandible intervertebral disc spacer through the dilator to the discspace; expanding the disc spacer to enlarge the disc space to a seconddesired height; inserting a bone matrix compound through the dilator tothe disc space; removing the dilator; and closing the incision.
 8. Themethod of claim 7, further comprising repeating each step in the discspace on a second lateral side of the patient's spine.
 9. The method ofclaim 8, wherein the guide needle, the dilators, the disc spacer and thebone matrix compound are inserted posteriorly of the spine.
 10. Themethod of claim 8, wherein the step of expanding the disc spacerenlarges an anterior side of the disc space a greater distance than theposterior side of the disc space to restore lordosis.
 11. An expandibleintervertebral disc spacer for implantation in a disc space to enlargethe height of the disc space and restore lordosis in a spine of apatient during interbody fusion procedures, comprising: a top portionhaving an inner surface and an outer surface, and having a first end anda second end; a bottom portion having an inner surface and an outersurface, and having a first end and a second end, the inner surface ofthe bottom portion facing the inner surface of the top portion; aplurality of pins joining the top portion to the bottom portion topermit vertical movement of the top portion with respect to the bottomportion; the inner surface of the top portion and the inner surface ofthe bottom portion defining a tapered bore having a diameter at a firstend that is greater than a diameter at a second end; and a rod forinsertion into the tapered bore to expand a distance between the topportion and the bottom portion, the second end of the top portion movinga greater distance with respect to the second end of the bottom portionthan the first end.
 12. The disc spacer of claim 11, wherein the taperedbore is threaded along at least a portion of its length.
 13. The discspacer of claim 12, wherein the rod is threaded.
 14. The disc spacer ofclaim 11, wherein the top portion and bottom portion are constructed ofbone material.
 15. The disc spacer of claim 11, wherein the outersurface of the top portion and the outer surface of the bottom portionare scored to enhance adherence to vertebra of the spine.
 16. A kit forperforming percutaneous interbody fusion surgical procedures,comprising: at least one expandible intervertebral disc spacer; at leastone guide needle; a plurality of dilators, a first dilator having aninner diameter that is slightly larger than an outer diameter of theguide needle, and each dilator having an inner diameter successivelylarger than an outer diameter of a previous dilator; and a packageincluding a top cover and a bottom cover, the top cover and the bottomcover forming a package containing the at least one disc spacer, the atleast one guide needle, and the plurality of dilators.
 17. The kit ofclaim 16, further comprising a tool for delivering the at least one discspacer through one of the dilators to an intervertebral disc space. 18.The kit of claim 17, further comprising a bone matrix material.
 19. Thekit of claim 16, wherein the package is sterilized after assembly. 20.An expandible intervertebral disc spacer, comprising: a split cylinderhaving a top half and a bottom half joined by a plurality of pins topermit movement of the top half with respect to the bottom half, aninner surface of the top half and an inner surface of the bottom halffacing each other defining a tapered bore extending from a first end ofthe cylinder towards a second end of the cylinder; and a piston screwinsertable into the tapered bore to expand the cylinder by moving thetop half away from the bottom half; wherein the piston screw moving intothe taperd bore causes the second end of the cylinder to expand agreater distance than the first end.